Correcting image distortion
The Lens Correction filter fixes common camera lens flaws, such as barrel and pincushion distortion, vignetting, and chromatic aberration. Barrel distortion is a lens defect that causes straight lines to bow out toward the edges of the image. Pincushion distortion is the opposite effect, where straight lines bend inward. Vignetting occurs when the edges of an image, especially the corners, are darker than the center. Finally, chromatic aberration appears as a color fringe along the edges of image objects.Some lenses exhibit these defects depending on the focal length or the f-stop used. You can have the Lens Correction filter use settings based on the camera, lens, and focal length used to make the image. You can also use the filter to rotate an image or fix image perspective caused by vertical or horizontal camera tilt. The filter's image grid makes these adjustments easier and more accurate than using the Transform command.In this exercise, you will adjust the lens distortion in an image of a Greek temple.
| 1. | Click the Go to Bridge button ( ). In Bridge, click the Lessons folder favorite(if it is not already selected), and then double-click on the Lesson08 folder. Locate the 08D_Start.psd image, and double-click to open it in Photoshop. Notice how the columns bend toward the camera and appear warped. This distortion was caused because the photo was shot at too close range with a wide-angle lens. | | 2. | Choose Filter > Distort > Lens Correction. The image appears in the Lens Correction dialog box with a large interactive preview, an alignment grid overlay, and options at right for removing distortion, correcting chromatic aberration, removing vignettes, and transforming perspective. | | 3. | In the Lens Correction dialog box, do the following:Drag the Remove Distortion slider to about +52.00 to remove the barrel distortion in the image. Or, select the Remove Distortion tool ( ) and drag in the image preview area to accomplish this, watching the Remove Distortion slider to see when you reach +52.00. | Watch the alignment grid as you make these changes so that you can see when the vertical columns are straightened in the image. |
Choose Edge > Transparency if it is not already chosen.Drag the Scale slider to 146%. | | 4. | Click OK to apply your changes and close the Lens Correction dialog box. The curving distortion caused by the wide-angle lens and low shooting angle are eliminated. | | 5. | (Optional) To see the effect of your change in the main image window, press Ctrl-Z (Windows) or Command-Z (Mac OS) twice to undo and redo the filter.Now you'll save the image for your PDF portfolio. | | 6. | Choose File > Save As. In the Save As dialog box, name the file columns_final.psd and save it in the Lesson08/Portfolio folder. Then, close the image window. |
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